CVE-2017-15405 in Chrome
Summary
by MITRE
Inappropriate symlink handling and a race condition in the stateful recovery feature implementation could lead to a persistance established by a malicious code running with root privileges in cryptohomed in Google Chrome on Chrome OS prior to 61.0.3163.113 allowed a local attacker to execute arbitrary code via a crafted HTML page.
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Analysis
by VulDB Data Team • 04/26/2020
The vulnerability identified as CVE-2017-15405 resides within the cryptohomed component of Chrome OS, specifically affecting versions prior to 61.0.3163.113. This flaw represents a critical security issue that exploits improper symlink handling combined with a race condition in the stateful recovery feature implementation. The vulnerability occurs at the intersection of file system operations and privilege escalation mechanisms, creating a pathway for malicious actors to establish persistent access within the operating system environment.
The technical implementation of this vulnerability stems from how cryptohomed manages symbolic links during stateful recovery operations. When the system attempts to recover state information, it processes symbolic links without adequate validation of their target paths, creating a window where malicious code can manipulate the symlink resolution process. The race condition aspect emerges from the timing gap between when the system checks for the existence of certain files and when it actually operates on them, allowing an attacker to substitute a legitimate file with a malicious symlink during this brief window. This combination creates a scenario where a local attacker with root privileges can manipulate the recovery process to execute arbitrary code with elevated privileges, effectively bypassing the system's security controls.
The operational impact of this vulnerability extends beyond simple code execution to encompass persistent system compromise. Once exploited, the malicious code can establish a foothold that survives system reboots, as the stateful recovery mechanism is designed to maintain system state across reboots. This persistence capability makes the vulnerability particularly dangerous in environments where Chrome OS serves as the primary operating system, as it allows attackers to maintain long-term access without requiring repeated exploitation attempts. The attack vector through crafted HTML pages demonstrates how web-based delivery mechanisms can be leveraged to compromise even sandboxed environments, highlighting the importance of comprehensive input validation across all system components.
Mitigation strategies for this vulnerability require immediate patching of affected Chrome OS versions to 61.0.3163.113 or later, which addresses the symlink handling and race condition issues through proper validation mechanisms and synchronization primitives. System administrators should implement comprehensive monitoring for unauthorized file system changes during recovery operations and establish strict access controls for the cryptohomed service. The vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities, and maps to ATT&CK technique T1059 for command and scripting interpreter, as well as T1068 for exploit for privilege escalation. Organizations should also consider implementing additional security controls such as mandatory access controls and file integrity monitoring to prevent similar issues in other system components that may exhibit similar race condition vulnerabilities.